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.\" groff -man -Tascii opusenc.1
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.TH opusenc 1 2019-09-07 "Xiph.Org Foundation" "opus-tools"
.SH NAME
opusenc \(en encode audio into the Opus format
.SH SYNOPSIS
.B opusenc
[
.I options
]
.I input_file
.I output.opus
.SH DESCRIPTION
.B opusenc
reads audio data in Wave, AIFF, FLAC, Ogg/FLAC,
or raw PCM (integer or floating point) format
and encodes it into an Ogg Opus stream.
If the input file is "\fB\-\fR" audio data is read from stdin.
Likewise, if the output file is "\fB\-\fR" the Ogg Opus stream
is written to stdout.
.PP
Unless quieted
.B opusenc
displays statistics about the encoding progress.
.SH OPTIONS
.SS "General options"
.TP
.BR -h ", " --help
Show command help.
.TP
.BR -V ", " --version
Show version information.
.TP
.B --help-picture
Show help on attaching album art.
.TP
.B --quiet
Enable quiet mode.
No messages are displayed.
.SS "Encoding options"
.TP
.BI --bitrate " N"
Set target bitrate in kbit/s (6\(en256 per channel).
.IP
In VBR mode this specifies the average rate for a large and diverse
collection of audio.
In CVBR and Hard-CBR mode it specifies the specific output bitrate.
.IP
The default for input with a sample rate of 44.1 kHz or higher is
64 kbit/s per mono stream and 96 kbit/s per coupled pair.
.TP
.B --vbr
Use variable bitrate encoding (default).
In VBR mode the bitrate may go up and down freely depending on the content
to achieve more consistent quality.
.TP
.B --cvbr
Use constrained variable bitrate encoding.
Outputs a specific bitrate.
This mode is analogous to CBR in AAC and MP3 encoders and managed mode in
Vorbis coders.
This delivers less consistent quality than VBR mode but consistent bitrate.
.TP
.B --hard-cbr
Use hard constant bitrate encoding.
With hard-cbr every frame will be exactly the same size, similar to how
speech codecs work.
This delivers lower overall quality but is useful where bitrate changes
might leak data in encrypted channels or on synchronous transports.
.TP
.B --music
Override automatic detection and tune low bitrate encoding for music.
By default, music is detected automatically and the classification
may vary over time.
.IP
Tuning impacts lower bitrates that involve tradeoffs between speech
clarity and musical accuracy, and has no impact at bitrates typically
used for high quality music encoding.
.TP
.B --speech
Override automatic detection and tune low bitrate encoding for speech.
By default, speech is detected automatically and the classification
may vary over time.
.IP
Tuning impacts lower bitrates that involve tradeoffs between speech
clarity and musical accuracy, and has no impact at bitrates typically
used for high quality music encoding.
.TP
.BI --comp " N"
Set encoding computational complexity (0\(en10, default: 10).
Zero gives the fastest encodes but lower quality, while 10 gives the
highest quality but slower encoding.
.TP
.BI --framesize " N"
Set maximum frame size in milliseconds (2.5, 5, 10, 20, 40, 60, default: 20).
Smaller framesizes achieve lower latency but less quality at a given bitrate.
Sizes greater than 20\ ms are only interesting at fairly low bitrates.
.TP
.BI --expect-loss " N"
Set expected packet loss in percent (default: 0).
.TP
.B --downmix-mono
Downmix to mono.
.TP
.B --downmix-stereo
Downmix multichannel speaker configurations to stereo.
.TP
.B --no-phase-inv
Disable use of phase inversion for intensity stereo.
This trades some stereo quality for a higher quality mono downmix,
and is useful when encoding stereo audio that is likely to be downmixed
to mono after decoding.
.TP
.BI --max-delay " N"
Set maximum container delay in milliseconds (0\(en1000, default: 1000).
.SS "Metadata options"
.TP
.BI --title " TITLE"
Set the track title comment field to
.IR TITLE .
.TP
.BI --artist " ARTIST"
Set the artist comment field to
.IR ARTIST .
This may be used multiple times to list contributing artists individually.
Note that some playback software does not display multiple artists gracefully.
.TP
.BI --album " ALBUM"
Set the album or collection title field to
.IR ALBUM .
.TP
.BI --genre " GENRE"
Set the genre comment field to
.IR GENRE .
This option may be used multiple times to tag a track with
multiple overlapping genres.
.TP
.BI --date " YYYY-MM-DD"
Set the date comment field to
.IR YYYY-MM-DD .
This may be shortened to
.I YYYY-MM
or
.IR YYYY .
.TP
.BI --tracknumber " N"
Set the track number comment field to
.IR N .
.TP
.BI --comment " TAG" = VALUE
Add an extra comment.
This may be used multiple times.
The argument should be in the form
.IR TAG = VALUE .
See the vorbis-comment specification
<https://\:www.\:xiph.\:org/\:vorbis/\:doc/v-\:comment.\:html>
for well known tag names.
.TP
\fB--picture\fR \fIFILENAME\fR | \fISPECIFICATION\fR
Attach album art for the track.
JPEG and PNG image formats are accepted.
Either a
.I FILENAME
for the artwork or a more complete
.I SPECIFICATION
form can be used.
The picture is added to a
.B METADATA_BLOCK_PICTURE
comment field similar to what is used in FLAC.
.IP
The
.I SPECIFICATION
is a string whose parts are separated by
.B |
(pipe) characters.
Except for the filename all parts are optional.
A plain
.I FILENAME
is equivalent to a
.BI |||| FILENAME
specification.
.IP
The format of
.I SPECIFICATION
is:
\%[\,\fITYPE\/\fR]\|\fB|\fR\|[\,\fIMEDIATYPE\/\fR]\|\fB|\fR\|[\,\fIDESCRIPTION\/\fR]\|\fB|\fR\|[\,\fIDIMENSIONS\/\fR]\|\fB|\|\fIFILENAME\fR
.IP
.PD 0
.I TYPE
is a number denoting the nature of the picture (default 3):
.RS
.RS 4
.TP
.B 0
Other
.TP
.B 1
32x32 pixel 'file icon' (PNG only)
.TP
.B 2
Other file icon
.TP
.B 3
Cover (front)
.TP
.B 4
Cover (back)
.TP
.B 5
Leaflet page
.TP
.B 6
Media (e.g., label side of a CD)
.TP
.B 7
Lead artist/lead performer/soloist
.TP
.B 8
Artist/performer
.TP
.B 9
Conductor
.TP
.B 10
Band/Orchestra
.TP
.B 11
Composer
.TP
.B 12
Lyricist/text writer
.TP
.B 13
Recording location
.TP
.B 14
During recording
.TP
.B 15
During performance
.TP
.B 16
Movie/video screen capture
.TP
.B 17
A bright colored fish
.TP
.B 18
Illustration
.TP
.B 19
Band/artist logotype
.TP
.B 20
Publisher/studio logotype
.RE
.RE
.IP
There may only be one picture each of type 1 and 2 in a file.
.PD
.IP
The default
.I DESCRIPTION
is an empty string.
.I FILENAME
is the path to the picture file to be imported.
.I MEDIATYPE
and
.I DIMENSIONS
are obtained from the file and any specified values are ignored.
.IP
More than one
.B --picture
option can be specified to attach multiple pictures.
.TP
.BI --padding " N"
Reserve
.I N
extra bytes for metadata tags.
This can make later tag editing more efficient.
Defaults to 512.
.TP
.B --discard-comments
Don't propagate metadata tags from the input file.
.TP
.B --discard-pictures
Don't propagate pictures or art from the input file.
.SS "Input options"
.TP
.B --raw
Interpret input as raw PCM data without headers.
.TP
.B --raw-float
Interpret input as raw floating point data without headers.
.TP
.BI --raw-bits " N"
Set bits/sample for raw input (default: 16; 32 for floating point).
May be 8, 16, or 24 for integer PCM or 32 for floating point.
.TP
.BI --raw-rate " N"
Set sampling rate for raw input (default: 48000).
.TP
.BI --raw-chan " N"
Set number of channels for raw input (default: 2).
.TP
.BR --raw-endianness " " 0 | 1
Set the endianness for raw input: 1 for big endian, 0 for little (default: 0).
.TP
.B --ignorelength
Ignore the data length in Wave headers.
The length will always be ignored when it is implausible (very small or very
large), but some stdin usage may still need this option to avoid truncation.
.SS "Diagnostic options"
.TP
.BI --serial " N"
Force use of a specific stream serial number, rather than one that is
randomly generated.
This is used to make the encoder deterministic for testing and is not
generally recommended.
.TP
.BI --save-range " FILENAME"
Save check values for every frame to a file.
.TP
\fB--set-ctl-int\fR [\,\fIS\/\fB:\fR]\,\fIX\/\fR=\,\fIY\fR
Pass the encoder control
.I X
with value
.I Y
(advanced).
Preface with
.IR S :
to direct the ctl to multistream stream number
.IR S .
This may be used multiple times.
.SH EXAMPLES
Simplest usage.
Take input as input.wav and produce output as output.opus:
.RS 5
opusenc input.wav output.opus
.RE
.PP
Produce a very high quality encode with a target rate of 160 kbit/s:
.RS 5
opusenc --bitrate 160 input.wav output.opus
.RE
.PP
Record and send a live stream to an Icecast HTTP streaming server using oggfwd:
.RS 5
arecord -c 2 -r 48000 -twav - | opusenc --bitrate 96 - - | oggfwd icecast.somewhere.org 8000 password /stream.opus
.RE
.SH NOTES
While it is possible to use opusenc for low latency streaming (e.g. with
.B "--max-delay 0"
and netcat instead of Icecast) it's not really designed for this, and the
Ogg container and TCP transport aren't the best tools for that application.
Shell pipelines themselves will often have high buffering.
The ability to set framesizes as low as 2.5\ ms in opusenc mostly exists
to try out the quality of the format with low latency settings, but not
really for actual low latency usage.
Interactive usage should use UDP/RTP directly.
.SH AUTHORS
Gregory Maxwell <greg@xiph.org>
.SH SEE ALSO
.BR opusdec (1),
.BR opusinfo (1),
.BR oggfwd (1)
